Lanthanopolyoxometalate‐Silica Core/Shell Nanoparticles as Potential MRI Contrast Agents

Abstract The NMR relaxivities of the decatungstolanthanoate core‐shell nanoparticles, prepared by encapsulating [Ln(W 5 O 18 ) 2 ] 9− polyoxometalates (LnPOM) within amorphous silica shells (K 9 ]@SiO ), were studied along Ln series. relaxivity GdPOM is slightly higher than for Gd‐DTPA due to second‐sphere relaxation effects, but values other paramagnetic LnPOMs are much smaller short T 1e their 3+ ‐ions. NPs have spherical structures, with LnPOM‐containing cores 9.5–28 nm diameters, and 4.0–11.0 thick shells. In water suspensions, negative zeta potentials (−32.5 −40.0 mV) time‐dependent hydrodynamic diameters (31–195 nm) reflecting formation aggregates. GdPOM@SiO suspensions ( r 1 =10.97 (mM Gd) −1 s , =12.02 0.47 T, 25 °C) considerably larger solutions, indicating that shell significantly porous water. This increase limited agglomeration complexes in core, limiting access those at core surface. Replacing half Gd ions Eu decreases 20 % 35 initial values, which still considerable, does not affect efficient luminescence properties centers. indicates mixed potential as dual modality MRI/optical imaging contrast agents.